First and Only Visible Supermoon of 2017 Shines This Weekend

From Sunday night into Monday morning, Dec. 3, the moon will shine up to 16 percent brighter and 7 percent larger than normal.

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Because the moon's orbit of the Earth is not perfectly circular, it is somewhat elongated, its distance from us varies.

That means the moon changes its distance to Earth by a few thousand miles over time, reaching a closest point (perigee) and a farthest point (apogee) in any given month. A supermoon occurs when the closest point to Earth in the moon's orbit coincides with a full moon.

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This makes the moon appear larger and brighter in the sky than usual. Look for it at 1 a.m. on Monday morning to see the moon at its nearest distance to Earth --222,443 miles. (Usually, the moon averages about 252-thousand miles. To see the supermoon at its most vivid, try to catch a glimpse just after sunrise. A phenomenon called the "moon illusion" makes the moon look much larger than at its peak height.